Fluid cushion



Oct. 26, 1965 P. CARR 3,213,760

FLUID CUSHION Filed 001?. 23, 1963 K W 2 I6 I2 3/ 3o Z 20 r 44 45 3 F a 4 ///lW/ 4 4i 4 1 2 46 ii, Fig. 2 F 0- 3 PAUL cAggENTOR X w/W United States Patent 3,213,760 FLUID CUSHION Paul Carr, Uniontown, Ohio, assignor to Flo-Tork, Inc. Filed Oct. 23, 1963, Ser. No. 318,267 3 Claims. (Cl. 91-395) This invention relates generally to fluid actuators, and more specifically to new and improved piston cushioning structure for fluid actuators.

An object of the invention is to provide a dependable and yet relatively simple device for cushioning relative movement between the cylinder and piston of a fluid actuator.

Another object of the invention is to provide new and improved structure in fluid actuators which is effective to cushion piston movement in one direction and to assure quick reversal of the piston stroke for movement in the opposite direction.

A further object of the invention is to provide structure as described above which is operable to cushion piston movement in a controllable manner.

Still another object of the invention is to provide structure as described above which is operable to cushion piston movement in a controllable manner.

Still another object of the invention is to provide cushioning structure having all of the foregoing features which is inexpensive, compact, and maintenance-free. 1

In general, the preferred embodiment of the invention contemplates a cushion head which forms an end wall of a fluid actuator cylinder. The cushion head is provided with a main fluid passage through which fluid is introduced to drive the piston of the actuator in one direction and with a by-pass passage through which fluid is exhausted during cushioning of the piston stroke in the opposite direction. The piston in the cylinder carries a cushion check which closes the main fluid passage when the piston reaches a predetermined point in its travel toward the cushion head.

When the cushion check closes the main fluid passage in the head, continued movement of the piston forces fluid from the cylinder through the by-pass passage. Preferably, a needle or equivalent device is provided for controlling the orifice size of the by-pass passage. By adjusting this needle, the speed of cushioning and the amount of energy absorbed can 'be readily controlled until the piston is bottomed against the inner face of the cushion head.

An important feature of the invention is the construction and operation of the cushion check which assures quick reversal of piston movement after it has been cushioned against the head. As will be hereinafter described in detail, the cushion check operates to open the main fluid passage orifice when fluid under predetermined pressure is introduced in the passage to drive the piston away from the head. This automatic opening of the main fluid passage allows full fluid flow into the cylinder. In addition to obtaining rapid reverse movement of the piston, the cushion structure provided by this invention eliminates the costly and less dependable check valves which are common in conventional cushioning arrangements.

Other objects and advantages of the invention will become apparent from the following detailed description and the accompanying drawing.

In the drawings:

FIGURE 1 is a cross-sectional view of a portion of a fluid actuator embodying the present invention;

FIGURE 2 is a cross-sectional, fragmentary view of a portion of the apparatus shown in FIG. 1; and

FIGURE 3 is a view similar to FIG. 2 and shows the apparatus in a different position of actuation.

3,213,760 Patented Oct. 26, 1965 Referring now to the drawing, the hydraulic rotary actuator embodying the present invention is generally designated by reference numeral 10. The actuator 10 may be of the general construction disclosed in assignees application Serial No. 258,824, filed February 16, 1963, now Patent No. 3,156,160, and entitled Actuator. As is described in greater detail in the referenced application, the actuator 10 may be symmetrical about its transverse center line, and for this reason only one end portion has been illustrated and described below.

The illustrated actuator 10 includes a central actuator body 11 having a gear chamber 12 in which a pinion 13 is disposed. The pinion 13 is mounted on an output shaft 14 which is suitably journaled in the actuator body 11. A cylinder 15 extends through the actuator body and a piston 16 is reciprocally mounted in the cylinder.

As shown, the actuator 10 further includes a piston rod 17 which is integral with the piston 16 and which constitutes a rack having teeth 18. The cylinder 15 is provided with a side opening 19 in communication with the gear chamber 12, and the pinion 13 extends through this opening in driven engagement with the teeth 18. With the illustrated arrangement, actuation of piston 16 to the left, as viewed in FIG. 1, serves to rotate the pinion and output shaft counterclockwise, while actuation of piston (not shown) on the opposite end of the rack 17 to the right serves to rotate the pinion and shaft clockwise.

In accordance with this invention, the end wall of the cylinder 15 is formed by a cushion head 20. An O-ring 21 is carried on the inner end of the cushion head 20 in sealing engagement with the inner wall of the cylinder. The cushion head 20 has a main fluid passage 22 and a by-pass passage 23. The main fluid passage 22 has an orifice through the inner face 25 of the cushion head, and a tapered plunger seat 26 (FIG. 3) is formed in the head around the orifice.

In the embodiment shown, the by-pass passage 23 includes a portion 27 which communicates with the main fluid passage 22 between the ends of the cushion head 20. A needle 28 is threadedly engaged in the head with the tapered end 28a'of the needle in the portion 27 of the by-pass passage. By axially adjusting the needle 28, it will be seen that the effective size of the by-pass passage can be controlled. In order to protect the needle 28 in its adjusted position, there preferably is provided a seal member 30 and a binder head screw 31 which is threaded into the capped hole 29.

The piston 16 carries an O-ring 40 in sealing engagement with the inner wall surface of the cylinder 15. The end of the piston 16 confronting the cushion head 20 is formed with a recess 41 in which is mounted the cushion check 42. As shown, the cushion check 42 comprises a hollow plunger having a closed, tapered outer end 43 conforming to the tapered plunger seat 26' and an open inner end around which is formed a radial flange 44. The flange 44 is in sliding engagement with the walls of the recess 41 and guides the cushion check for reciprocal movement so that its tapered end 43 is aligned with the plunger seat 26.

The plunger also is formed with side wall ports 45.- The ports 45 open through the walls of the plunger between the flange 44 and the tapered end 43. With this construction the inside of the plunger is in fluid engagement with the cylinder chamber and any fluid that otherwise would be tapered in the recess 41 by inward movement of the plunger can escape through the ports 45 into the cylinder chamber. A compression spring 46 is mounted between the bottom of the recess and the closed end of the plunger so that it normally extends from the piston 16 toward the cushion head 20. Preferably, the mouth 48 of the hollow plunger or cushion check 42 is flared radially outwardly so reciprocal movement of the plunger is not impaired by engagement with an intermediate portion of the spring 46 and, so that the spring can be readily inserted in the plunger. The inner end of the plunger is maintained in the recess 41 by a retaining ring 47 which is mounted at the mouth of the recess so as to engage the radial flange 44.

As generally described, the cushioning operation is initiated at a predetermined point in the travel of the piston 16 toward the cushion head 20. At this point which is illustrated in FIG. 1, the closed tapered end 43 of the normally extending cushion check 42 engages the plunger seat 26 to close the orifice of the main fluid passage 22. Continued movement of the piston to the position shown inFIG. 2 forces fluid from the cylinder 11 through the by-pass passage 23 so that the speed of the cushioning and the amount of energy absorbed can be controlled by suitable adjustment of the needle 28. During thiscushioning action, the spring 46 is compressed to allow the cushion check 42 to recede into the recess 41. Any fluid that may become trapped in the recess by the cushion check is free to escape through the ports 45 into the cylinder. The size of the ports 45 may be made to restrict fluid flow from the recess 41. In this manner a cushioning of the piston stroke is assured even though the needle 28 is improperly adjusted or temporarily ineflective for any reason.

The outer end 50 of the main fluid passage 22 is adapted to be connected to any suitable source of fluid under pressure so that the piston can be driven away from the cushion head. In order to obtain automatic, rapid reversal of piston movement after the cushioning action, it is preferable to make the depth of the recess 41 at least equal to the length of the plunger 42. With this preferred construction, the plunger is able to move a suflicient distance into the recess 41 (FIG. 3) to unseat itstapered end 43 after the piston is against the cushion head and the fluid pressure in the main passage reaches a necessary amount to overcome the spring 46. In this manner, full fluid flow into the cylinder and quick reversal of the piston stroke is obtained. After the piston stroke has been reversed and the piston has been forced away from the cushion head, the spring 46 returns the cushion check 42 to its normal position for the next cushioning operation. Since the inside of the cushion check communicates with the cylinder chamber through the ports 45, the fluid pressure in the recess 41 is substantially the same asin the cylinder chamber. This balancing of the fluid pressure assures free movement and accurate positioning of the cushion check under the action of the spring 46.

It will thus be apparent that the invention obtains the objectives of providing new and improved structure capable of cushioning the stroke of a piston in a controlled manner and of operating to permit the piston stroke to be reversed quickly and automatically. The described cushioning structure is relatively simple and inexpensive and, at the same time, it is dependable in operation.

Another important advantage is that the cushioning structure of the invention can be embodied in fluid actuators of many different types and constructions. Hence, while the novel cushioning structure has been disclosed as embodied in a hydraulic rotary actuator, it is to be understood that the disclosed actuator is not limiting of the invention and that it has been selected solely for purposes of describing the operation and construction of the invention to those skilled in the art. 7 Many different modifications and variations of the invention will be apparent in light of the foregoing detailed disclosure. Therefore, it is to be understood further that, within the scope of the appended claims, the invention can be practiced otherwise than as specifically shown and described.

What is claimed is:

1. A fluid actuator comprising:

(a) an outer housing having an inner piston receiving bore;

(b) an end wall disposed transversely across one end of the piston receiving bore;

(c) a piston slidably mounted in said bore and being reciprocally movable toward and away from said end wall, an end of the piston, portions of the surface of the piston receiving bore, and the end wall defining a fluid chamber;

(d) said piston having inner surfaces defining a plunger receiving recess in said end;

(e) a plunger slidably disposed within the plunger receiving recess and being reciprocally movable within the recess between first and second positions relative to the piston, the plunger in said first position extending substantially out of the plunger receiving recess so as to define a fluid space between said plunger and the piston surfaces defining said plunger receiving recess, and said plunger in said second position being substantially received within the plunger receiving recess, whereby said fluid space is at a minimum;

(f) biasing means urging said plunger toward said first position;

(g) said end wall having a main fluid passage in alignment with said plunger and communicating with said fluid chamber;

(h) said end wall including a fluid by-pass passage communicating with said fluid chamber;

(i) means in said by-pass passage for metering the flow of fluid through said by-pass passage;

(j) said plunger and portions of the end Wall adjacent said main fluid passage having mating surfaces for closing communication between said fluid chamber and the main fluid passage when the mating surfaces are in abutment;

(k) said plunger having an imperforate transverse end surface for closing the main fluid passage when the mating surfaces are in abutment; and,

(1) said plunger including opening means on the piston side of said mating surfaces for providing restricted fluid flow between said fluid chamber and the fluid space whereby said mating surfaces about at a predetermined point in the travel of the piston toward the end wall and fluid trapped between said piston and said end wall is exhausted at a controlled rate through said by-pass passage to provide a cushion and fluid in said fluid space is restricted in flowing into said fluid chamber to provide an additional cushion, and said plunger is thereafter movable into said recess to open said main fluid passage when fluid is supplied through said main passage at a pressure exceeding the urging force of said biasing means.

2. The device of claim 1 wherein said recess has a depth substantially equal to the length of said plunger so that said plunger is movable substantially wholly within said piston against the urging of said bias means to separate said mating surfaces immediately upon the introduction of fluid under pressure into said main fluid passage and before the piston moves substantially.

3. A piston device comprising:

(a) a housing having an inner piston receiving chamber and an end wall disposed transversely across one end of the piston receiving chamber;

(b) a piston slidably mounted in the chamber and reciprocally movable toward and away from the end wall, said piston having an end abuttable with the end wall;

(c) said piston having a plunger receiving cavity in said end which is abuttable with the end wall;

((1) a plunger slidably disposed within the plunger receiving cavity and being reciprocally movable within the cavity;

(e) said end Wall having a main fluid passage aligned with said plunger;

(f) said end wall including a fluid by-pass passage spaced from the main passage;

(g) means in said by-pass passage for metering the flow of fluid through said by-pass passage;

(h) said plunger and portions of the end Wall around said main passage having mating surfaces for closing the main passage with said plunger having an imperforate end Wall within its mating surface such that when said mating surfaces are in abutment, the main passage is shut off by said plunger end wall;

(i) said plunger having three positions:

(1) the plunger when in the first position projecting from the piston;

(2) the plunger when in the second position having its mating surface in engagement with the end wall mating surface and the plunger being spaced from the bottom of the cavity; and,

6 (3) said plunger in the third position being nearer the bottom of the cavity than in the second position; and,

(3') said piston being in abutment with said end wall when the plunger is in the second position whereby when the piston is abutting the end wall and fluid under pressure is introduced to said main passage the plunger moves from its second position to its third position so as to immediately apply full fluid pressure to said end of the piston.

References Cited by the Examiner UNITED STATES PATENTS 2,755,755 7/56 Flick et al. 91395 2,769,429 11/56 Lencioni 91-395 3,054,385 9/62 Hanna 91395 3,067,726 12/62 Williams 91-395 FOREIGN PATENTS 451,779 10/48 Canada.

FRED E. ENGELTHALER, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,213,760

Paul Carr It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, lines 22 to 24, strike out "Still another object of the invention is to provide structure as described above which is operable to cushion piston movement in a controllable mannere"; column 2, line 67, for "tapered" read trapped column 6, line 14, for "2,755,755" read Signed and sealed this 21st day of June 1966.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer October 26, 1965 

1. A FLUID ACTUATOR COMPRISING: (A) AN OUTER HOUSING HAVING AN INNER PISTON RECEIVING BORE; (B) AN END WALL DISPOSED TRANSVERSELY ACROSS ONE END OF THE PISTON RECEIVING BORE; (C) A PISTON SLIDABLY MOUNTED IN SAID BORE AND BEING RECIPROCALLY MOVABLE TOWARD AND AWAY FROM SAID END WALL, AND END OF THE PISTON, PORTIONS OF THE SURFACE OF THE PISTON RECEIVING BORE, AND THE END WALL DEFINING A FLUID CHAMBER; (D) SAID PISTON HAVING INNER SURFACES DEFINING A PLUNGER RECEIVING RECESS IN SAID END; (E) A PLUNGER SLIDABLY DISPOSED WITHIN THE PLUNGER RECEIVING RECESS AND BEING RECIPROCALLY MOVABLE WITHIN THE RECESS BETWEEN FIRST AND SECOND POSITIONS RELATIVE TO THE PISTON, THE PLUNGER IN SAID FIRST POSITION EXTENDING SUBSTANTIALLY OUT OF THE PLUNGER RECEIVING RECESS SO AS TO DEFINE A FLUID SPACE BETWEEN SAID PLUNGER AND THE PISTON SURFACES DEFINING SAID PLUNGER RECEIVING RECESS, AND SAID PLUNGER IN SAID SECOND POSITION BEING SUBSTANTIALLY RECEIVED WITHIN THE PLUNGER RECEIVING RECESS, WHEREBY SAID FLUID SPACE IS AT A MINIMUM; (F) BIASING MEANS URGING SAID PLUNGER TOWARD SAID FIRST POSITION; (G) SAID END WALL HAVING A MAIN FLUID PASSAGE IN ALIGNMENT WITH SAID PLUNGER AND COMMUNICATING WITH SAID FLUID CHAMBER; 